Lava is lighting up the night sky at Halema'uma'u crater.

Since Thursday, a sloshing, surging pond of molten rock has illuminated the vent deep within Kilauea's summit.

"It's beautiful. The glow is bright from Halema'uma'u," said Jim Gale, Hawaii Volcanoes National Park's chief of interpretation.

Lava deep within the pit has been occasionally visible from an off-limits section of the park.

Since the first week in January, Kilauea has experienced a periodic interruption in its flow called a deflation-inflation event.

As the magma flows out of the volcano's plumbing it causes the summit to deflate by an amount that only instruments can detect.

When this happens, the lava pond retreats from the view of a Web cam perched at the edge of Halema'uma'u. Then, about a day or two later, lava entering the sea near Kalapana also stops.

The "inflation" part of the cycle occurs when the magma supply resumes, filling the summit as if it were a giant water bed. It's during the inflation of Kilauea that unusual events happen, like the rupture of a lava tube.

Throughout Thursday evening, the surface of the lava pond would sometimes rise to "very high levels," at one point within 400 feet of the crater floor.

Each time this happened, after hesitating for several minutes, the lava surface then rapidly dropped to its previous, lower level.

The normal depth of the lava pond is about 660 feet below the surface of the old crater. The pond appeared in November, although visitors to the summit overlook at the Thomas A. Jaggar Museum cannot see it directly.

Geologists Tim Orr, Matt Patrick and a volunteer spent about three hours at the old crater overlook, which was closed in early 2008 destroyed by an explosive eruption.

"It was very, very loud," Orr said. "Kind of a loud noise of lava spattering and sloshing around, and most of the time it was a lava river" that returned underground and resumed its journey to the sea.

Standing 820 feet above the lava's surface, "you could feel the radiant heat on your face," Orr said, but it wasn't uncomfortably hot.

He estimated the diameter of the pond at 230 to 330 feet across, or slightly smaller than Hilo Bay's Coconut Island.

By Friday morning, the vent had quieted down. A webcam perched at the edge of the pit showed a stable pond feeding lava into an underground conduit. A thin crust of solid rock develops on the pond's surface and then fractures as the underlying lava moves, creating mesmerizing patterns of black, yellow orange and red.

The renewed activity at the summit crater comes on the 50th anniversary of the destructive 1960 eruption at Kapoho.

Elsewhere on the volcano, lava has re-emerged from what is called the Thanksgiving Eve Breakout vent to the east of Pu'u 'O'o. Helicopter tour pilots have told Orr that lava has broken out of a tube and is creating a surface flow above the pali. The flow had not yet reached the ocean as of Friday evening.

"At least a part of the tube has been reoccupied," he said.